With current attempts at using wind energy for power generation, the method used commonly at present is to provide rotors with a horizontal rotating axis with radial rotor arms which work according to the principle of a windmill or propeller. The disadvantages of these rotors lie in the high level of noise generated and the required large investment arising from the necessity to provide high towers to install the rotors. In addition, these wind rotors which are known in the art require electrical generating equipment or similar to be mounted at the top of the tower unless costly transmissions are provided.
A further disadvantage of wind rotors with a horizontal rotational axis is that they can only work if the wind current approaches them at right angles. This means that the rotors must always be turned into the wind by special equipment.
Furthermore, the profile of the rotors known in the art is difficult and time-consuming to achieve with the result that they can generally only be manufactured at high cost.
Rotors of the type mentioned in the introduction are known, for example, as Darrieus rotors. These rotors consist of approximately hyperbolically curved rotor blades attached to a vertical rotating axis. By their very nature, however, these rotors are not self-starting. This means that they must be started by a servomotor. Moreover, useful power is only generated at wind speeds above 5 m/s if Darrieus rotors are used.
Another vertical rotor known in the art is the so-called Savonius rotor. This, however, has a very large area exposed to the wind, as a result of which it is at great risk from storms. For this reason it is generally used on a small scale as a ventilator for the inside of enclosed vehicles where it is roof-mounted.
Rotors of the type mentioned in the introduction are also known in the art for measuring wind strengths. The generic aerodynamic profile for these is formed by open semi-spherical dishes. These rotors too offer a large surface area to the wind with the result that, when scaled up, they are unsuitable for energy generation.
A wind collector blade for a horizontal turbine rotating about a vertical axis was described in German Patent 3 517 752 C 2. This wind collector blade consists of two wing profiles which were positioned adjacent to each other at a given radial spacing, connected by arms and which encompassed a through-flow duct. The two wing profiles with their outer face contours are formed as parts of the outer face contour of a thick, self-starting wing profile, and the wing profiles with their straight, parallel or approximately parallel inner flanks delimit the through-flow duct mentioned above. Although this already known vertical rotor, in contrast to the Darrieus rotor, permits self-starting even at relatively low wind speeds, its rotation is unnecessarily hindered by the through-flow duct formed between the two wing profiles. In addition, the design of this rotor is very complicated because of the complex flow through and around it, and the manufacture of the rotor blades, particularly the relative location of the wing profiles to each other, is very demanding.
A generic wind turbine tower is known in the art from U.S. Pat. No. 4,430,044 where horizontal rotor arm sections and vertical rotor arm sections located at right angles to these at their ends are provided. In the case of this already known configuration of the rotor blades it is necessary, particularly for self-starting by the rotor, to design the rotor blade sections such that their alignment relative to the wind is adjustable. To this end, an elaborate control device is provided specially in accordance with this known state of the art. A means of controlling the angle of incidence of the rotor blades during operation is also required in order to be able to operate this known vertical turbine, and thus its own control system must be provided. Such vertical rotors are consequently unsuitable for self-assembly or for use in developing countries since in this case what are particularly required are easily constructed rotors without complicated control systems.
German Patent 3 529 474 A 1 describes a collapsible vertical windmill with four main sails in a rhombic configuration relative to each other. To assist the operation of this vertical windmill, auxiliary sails are provided in addition to the main sails. Furthermore, the individual sail arms are mounted on shafts which are connected with each other at the corners of the rotor via articulated joints. These articulated joints represent weaknesses in the overall rotor which have an adverse effect on the stability of the vertical windmill as a whole. Moreover, this vertical windmill too requires an elaborate control system.
A vertical wind rotor is known from U.S. Pat. No. 4,561,826 whose rotor arms can pivot during rotation about the horizontal axis such that the rotor arms can be moved from an alignment diagonal to the vertical axis as far as the horizontal. This requires a complex construction for the rotor as a whole or the use of, on the one hand, flexible and resilient materials in the manufacturing process and, on the other, materials in the manufacture of the rotor arms which can withstand constant stresses.